\[\boxed{\mathbf{1142}\mathbf{\text{.\ }}Еуроки\ - \ ДЗ\ без\ мороки}\]
\[x_{1} = 5x_{2}\]
\[x^{2} - bx + 20 = 0\]
\[x_{1}x_{2} = 20\]
\[5x_{2}^{2} = 20\]
\[x_{2}^{2} = 4,\ \ \]
\[x_{2} = 2,\ \ x_{2} = - 2\]
\[x_{1} = 10,\ \ x_{1} = - 10\]
\[x_{1} + x_{2} = b\]
\[b = 12;\ \ b = - 12.\]
\[Ответ:x_{1} = 10,\ x_{2} = 2,\ b = 12\ \ \ \ \]
\[или\ \ x_{1} = - 10,\ x_{2} = - 2,\ b = 12.\]